When performing surgery to insert vertebral fixation rods for spinal fusion, there is a need to ensure that the fusion rod is passed accurately between the tulips of the pedicle screws, before the screws are tightened onto the rod. This can be a problematic task since the spine may be severely deformed in a scoliotic patient, and even in a non-scoliotic patient, adjacent vertebrae generally have differing protrusion heights and are not linearly aligned because of the natural spinal lordosis. Reference is made to FIG. 1 which illustrates such a typical vertebral fixation rod implementation, in which the rod 11 had been given a curvature to match the lordosis curvature of the spine 10. In currently used procedures, the surgeon generally bends the fusion rod during the operation, typically using manual tools, so that it matches the positions of the tulips 12 of the pedicle screws, using his/her visual judgment in order to ensure that the rod fits accurately between the heads 12 of the various screws. However this procedure is prone to inaccuracies and since a typical fusion rod is intended to be a high strength component and is generally made of titanium or stainless steel and is typically 5 mm in diameter, the surgeon often has to exert considerable force using pliers to bend the rod appropriately during connection, in order to ensure that the rod fits without exerting undue pressure on the patient's vertebrae.
In US Patent Application Publication No. 2005/0262911 to H. Dankowicz et al, for “Computer Aided Three-Dimensional Bending of Spinal Rod Implants, other Surgical Implants and other Articles, Systems for Three-Dimensional Shaping, and Apparatuses Therefore”, there is described a computer aided system for bending an implantable rod three-dimensionally, which is especially useful for pre-surgical formation of implantable spinal rods. Such a system may also use imaging performed intraoperatively on the surgical site, especially to determine the position of pedicle screw heads (tulips) to which the rod is to be attached, in order to determine the shape of the rod to be formed. However, in order to perform intra-operative bending of the rod to match the desired shape in 3D, this system requires the generation of additional images during the procedure, which subjects the patient and possible also the medical staff, to additional radiation exposure.
Therefore, there is a need for an apparatus and procedure which will enable the surgeon to accurately and easily shape a vertebral fixation rod during the surgical procedure, without the need for additional imaging to determine the shape the rod has to be given.
Additionally, although such rod assemblies may be used to fuse two adjacent vertebrae, there are often cases of scoliosis and severe deformities where the region of the spine to be treated may include even 10 or more vertebrae. Such a long construction may be used to rigidly connect all the vertebrae within the desired range, but in certain cases there is no need to fuse all the levels and some vertebra should not be fused together in order to preserve their relative motion. Hence there is also a need for a rod that poses different compliances at different points in accordance with the fusion or dynamic stability needs of the spine.
There therefore exists a need for such devices and methods which overcomes at least some of the disadvantages of prior art systems and methods.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.